Abstract

Lattice parameters have been determined from high-resolution neutron-powder diffraction data collected as a function of temperature for perovskites in the Pr1−xLaxAlO3 solid solution in order to determine the influence of La doping on the Imma↔C2/m transition temperature, Tc∗. A plateau in Tc∗ at ∼150 K extends to x≈0.016±0.002, followed by a linear reduction with increasing LaAlO3 content. The plateau is interpreted in terms of a saturation effect such that there is a composition limit below which the strain fields surrounding individual La3+ ions are isolated in the PrAlO3 matrix and above which they overlap. On this basis the strain fields are estimated to have diameters of ∼16–18 Å, which appears to be a characteristic length scale for structural relaxation around dopant atoms and other types of local clusters in oxide perovskites.